Genetic variation of an Italian long shelf-life tomato (Solanum lycopersicon L.) collection by using SSR and morphological fruit traits

The recovery of ancient germplasm in tomato (Solanum lycopersicon L.) has become necessary to limit the wide genetic erosion caused by the employment of modern cultivars. Among germplasm collections, long shelf-life landraces could represent an important source of biodiversity. The present study provides a first set of molecular and phenotypic data on long shelf-life (so called "da serbo" in southern Italy) tomato collection, mainly originated from Sicily together with some landraces from Campania and Apulia. The analysis of fruit traits showed a low intra-varietal variation, while exhibiting a quite higher inter-varietal variability. Overall, the cultivars have been classified in six fruit shape classes of which flattened and slightly flattened included the 54.76 % of the collection. The principal component analysis (PCA) showed a large cluster in which almost all landraces from Sicily were included. The microsatellite (SSR) analysis confirmed a low intra-varietal variation, and the very low heterozygosity (H-o) revealed a high degree of homozygosity in these landraces. In accordance with limited morphological variability, the values of microsatellite polymorphism (PIC) showed a low genetic variability among these long shelf-life tomato cultivars. Cluster analysis based on 10 polymorphic SSR was not able to distinguish landraces for their different origin, while allowed to classify similar genotypes in four groups. Three groups showed a limited genetic distance while in a fourth largest and genetic variable cluster was included genotypes more selectable for traits of agronomic interest. Overall, the phenotypic and genetic variation allowed us to classify a collection of Sicilian long shelf-life tomato landraces.